Tropical forests cycle more CO2 and water than any other biome, and play critical roles in determining Earth’s energy balance. Intact tropical forests, likely Earth’s largest carbon sink, are susceptible to a warming climate. The 10-year vision for NGEE Tropics is to achieve dramatically reduced uncertainty in ESM projections, and increased scientific understanding of how tropical forest ecosystems will respond to climate and atmospheric change.

The largest flows of carbon between land and atmosphere come from terrestrial ecosystem photosynthesis and respiration, with potentially profound impacts on atmosphere and climate. The AmeriFlux Network, established in 1996, has more than 120 long-term flux sites, independently operated and funded, throughout the Western Hemisphere. The sites are diverse, ranging from the Amazonian rainforests to the North Slope of Alaska, and some span gradients in elevation or rainfall. Site researchers observe ecosystem level exchanges of CO2 and other greenhouse gases, water, and energy, to assess terrestrial ecosystems’ responses and feedbacks to the environment.